Ultrabright Red‐Emitting Photostable Perylene Bisimide Dyes: New Indicators for Ratiometric Sensing of High pH or Carbon Dioxide

Abstract

New pH‐sensitive perylene bisimide indicator dyes were synthesized and used for fabrication of optical sensors. The highly photostable dyes show absorption/emission bands in the red/near‐infrared (NIR) region of the electromagnetic spectrum, high molar absorption coefficients (up to 100 000 m −1 cm−1), and fluorescence quantum yields close to unity. The absorption and emission spectra show strong bathochromic shifts upon deprotonation of the imidazole nitrogen atom, which makes the dyes promising as ratiometric fluorescent indicators. Physical entrapment of the indicators into a polyurethane hydrogel enables pH determination at alkaline pH values. It is also shown that a plastic carbon dioxide solid‐state sensor can be manufactured by immobilization of the pH indicator in a hydrophilic polymer, along with a quaternary ammonium base. The influences of the plasticizer, different lipophilic bases, and humidity on the sensitivity of the sensor material are systematically investigated. The disubstituted perylene, particularly, features two deprotonation equilibria, enabling sensing over a very broad pCO2 range of 0.5 to 1000 hPa.

Optical Sensing and Imaging of pH Values: Spectroscopies, Materials, and Applications

“…PDIs 122 , 123 , 139 , 373 , 482 , 483 can be viewed as π-extended analogues of naphthalene diimides. However, even core-unsubstituted dyes absorb very efficiently in the green part of the spectrum and emit green-yellow light with QYs close to unity.…”

“…The absorption and emission of PDIs can be bathochromically shifted when the dyes are laterally extended in the bay region. 483 By condensation with benzo nitriles, one or two pH sensitive imidazole structures are attached to the perylene core. The indicator dyes feature molar absorption coefficients of around 80 000 M –1 cm –1 and quantum yields close to unity.…”

Organic–inorganic hybrid sol–gel materials doped with a fluorescent triarylimidazole derivative

“…Pfeifer et al prepared a polyurethane hydrogel with a pH-sensitive dye perylene bisimide functionalised with one or two imidazole moieties. 65 The protonation/deprotonation of the imidazole ring allows pH sensing at alkaline pH values. The abovementioned work by Nguyen et al reported an imidazole-based OFS that is sensitive to pH in the desired range for concrete applications, i.e., pH 10-13.…”

Perylene Diimide-Based Fluorescent and Colorimetric Sensors for Environmental Detection

“…Colorimetric sensing is of particular interest for environmental detection and monitoring because of its ease and simplicity of operation, low cost and expedient readout (even with naked eyes) without using additional instruments. PDI-based colorimetric sensors have been utilized for probing environmental factors such as humidity, solvent polarity, pH, and metal and non-metal ions, organic pollutants contained in environment [4][5][6]55]. Some PDI sensors were even used for producing biometric fingerprints [56].…”